This invention can be used in various fields where constructions are tested for continuity defects in not-so-easily accessible areas. Examples of device and method implementation may include pipes for oil and gas industry, detection of flaws in rolled products in metallurgical industry, welding quality of heavy duty equipment such as ships and reservoirs, etc. It is especially important for inspection of loaded constructions, such as pressured pipes, infrastructure maintenance, nuclear power plant monitoring, bridges, corrosion prevention and environment protection.
Similar to the modes of transportation like roads, railroads, and electric transmission lines, the pipelines have an important role in the nation's economy, belonging to the long linear assets. They typically cross large distances from the points of production and import facilities to the points of consumption. Like the other modes of transportation, pipelines require very large initial investment to be built, having long exploitation periods when properly maintained. Like any engineering structure, pipelines do occasionally fail. While pipeline rates have little impact on the price of a fuel, its disruptions or lack of capacity can constrain supply, potentially causing very large price spikes. That's why pipelines, such as ones used in the oil and gas industry, require regular inspection and maintenance before potentially costly failures occur.
The major causes of pipeline failures around the world are external interference and corrosion; therefore, assessment methods are needed to determine the severity of such defects when they are detected in pipelines. Pipeline integrity management is the general term given to all efforts (design, construction, operation, maintenance, etc.) directed towards ensuring continuing pipeline integrity.
Traditional method of assessing the structural integrity typically complemented by flaw detection using in-line inspection (ILI), detecting and evaluating various metal defects organized by area (clusters), assessing their danger by calculating a level of stress-deformed state (SDS), and deciding on a permissible operating pressure with evaluated factor of repair (EFR), based on residual pipe wall thickness (for defects of “metal loss”—corrosion type).
As a contact technique, pigging devices has been used for many years to maintain larger diameter pipelines in the oil industry. Today, however, the use of smaller diameter pigging devices is increasing in many plants as plant operators search for increased efficiencies and reduced costs. Unfortunately, the ILI using intelligent pigging is unavailable for a wide range objects that require full disruptive inspection and significant spending on repair preparation. While the ILI method is suitable for the initial flaw detection, it is less efficient for the relative degree (ranking) of the risk-factor evaluation, as well as for defective pipeline serviceability calculation.
Pipe-line pigging device can detect the following types of defects: i) changing in geometry: dents, wavy surface, deformed shape of cross-section; ii) metal loss, having mechanical, technological or corrosion nature; material discontinuity: layering and inclusions; iii) cracks; iv) all types of welding defects.
Pipe-line pigging is a very expensive and labor-consuming method. The major limitation of this method is the fact that a large part of pipe-lines are not prepared for the pigging device operation, e.g. due to lack of input/output chambers for pig-flow device launching and pipe-line cleaning access, partially blocked pipe cross-section due to the welding artifacts, geometrical abnormalities and large slopes (small radius turns) of the pipe-line layout. In order to make the pipe-line pigging method possible, a significant preparation has to be done in advance, in particular, the high residual level magnetization (saturated magnetic fields) of the pipe-line has to be performed before using the pig-flow device. This causes future technical problems of the pipeline demagnetization that required for actual pipe repair after the pigging.
Moreover, the evaluation of the absolute values of mechanical flaws by pigging device is particular difficult due to the multiple additional factors that have to be taken into account, e.g. bearing capacity of the soil, local cyclical loads (temperature, etc.).
Typically, a pipeline company will have a thorough pipeline safety program that will include a routine for the identification of pipeline defects and review of pipeline integrity. Such a plan should include, but not be limited to: i) a review of previous inspection reports by a third party expert; ii) excavation of sites identified by this review for visual examination of anomalies; iii) repairs as necessary; and iv) addressing factors in the failure and verify the integrity of the pipeline.
It is important to mention that the pipeline safety program can be only as effective as the interpretation of internal inspection reports.
There are several magnetographic devices that have been disclosed for non-destructive inspection of ferrous materials. In magneto-graphic inspection and defectoscopy the tested area of the material is placed in proximity to the magnetic medium. The changes of the surface-penetrating magnetic flux due to the material flows or deviations can be recorded. The resulting “magnetogram” of the material can provide the information about the location, size, and type of the defect or abnormality. In general, this information can be converted into the report about the quality of the material. Obtaining the magnetogram (magnetic picture) of the material in the course of the non-destructive inspection process is very challenging and typically requires additional forms of inspection, such as roentgenogram or an X-ray image.
For example, U.S. Pat. No. 4,806,862 (Kozlov) offers a contact method of magnetographic inspection of quality of materials, where a magnetic substance (such as liquid) is applied to be magnetized together with the tested material. According to the invention, the intensity of the magnetizing field is established by the maximum curvature of the surface of a drop of a magnetic fluid applied onto the surface of the material to be inspected, so that the resulting magnetogram can be used to assess the quality of the material.
In another magnetographic U.S. Pat. No. 4,930,026 (Kljuev), (also cf., USSR Inventor's Certificate No. 482,669, Cl. GOIN 27/89, published in “Biulleten Izobreteny” No. 32, 1975), the flaw sensor for magnetographic quality inspection is disclosed, which includes a flaw detector and a mechanism for driving the magneto-sensitive transducer. During the scanning procedure, the magnetic leakage fluxes penetrate through the surface of the material in places where flaws occur, resulting in a magnetogram of the tested material.
There is another magnetic technique has been proposed by U.S. Pat. No. 6,205,859 (Kwun) to improve the defect detection with magnetostrictive sensors for piping inspection. The method involves exciting the magnetostrictive sensor transmitter by using a relatively broadband signal instead of a narrow band signal typically used in order to avoid signal dispersion effects. The amplified detected signal is transformed by a short-time Fourier transform providing the identifiable signal patterns from either defects or known geometric features in the pipe such as welds or junctions. Underwater pipelines inspection by magnetosptictive sensors in described in U.S. patent application Ser. No. 13/336,302 by the authors of the present invention.
There is also a Russian technical standard (GOST), [P 102-008-2002], certifying the technical condition of the pipe-line based on the results of the remote magneto-metric measurements. The defect areas risk-factor criteria and ranking (such as material stress: F-value) is used for planning a required sequence of repair and maintenance steps. Such criteria were developed by comparison of a risk-factor calculated using the defect geometry in calibration bore pits with a predicted risk-factor obtained by the remote magneto-metric data (i.e. comprehensive F-value of particular magnetic anomaly).
The deviations of F-value can be classified as follows: X1—for negligible defects (good technical condition of the metal); X2—for defects that require a planned repairs (acceptable technical condition); X3—for defects that require immediate repairs (unacceptable, pre-alarm technical condition, alarm).
The absolute values X1-X3 of the F-value (comprehensive value of magnetic field anomaly) should be defined for each particular case, depending upon the following factors: i) Material (e.g. steel) type; ii) Topological location with the local background magnetic fields variation range, iii) Distance to the object (e.g. pipe-line installation depth), iv) General condition of the deformation-related tension within construction under testing, v) etc.
As a result, the only relative changes (variations) of the magnetic field can be evaluated for the given defective segment (relatively to the flawless segment), by comparison its relative F-values. Thus, the very moment of the ultimate stress-limit crossing can be identified for each defective segment during the real operation (i.e. under pressure/loaded) condition. It can be done by monitoring the development of the defects within its F-value interval, namely, starting from the good technical condition X1 up until the yield-strength-limit approaching and material breakdown. It provides a real possibility to predict the defect's speed development, resulting in increased accuracy in priority order definition for upcoming maintenance steps.
The aforementioned techniques are not satisfactory to be used for efficient prediction in defects development timeline and not capable of providing a real-time alert about the strength-limits approaching, i.e. when probable construction failure is about to occur.
The closest technology to the disclosed invention is shown in RU 2264617, describing the Magnetic Tomography (MT) technique of ‘Contactless Pipe-line Defect Discovering, Localization and Device Doing the Same’. This technique includes a remote magnetic field vectors measurement in Cartesian coordinates with the movement of measuring device (magnetometer) along the pipe-line, the recording of the anomalies of magnetic field (on top of background magnetic field), processing of the data and report on found pipe-line defects with their localization shown in resulting magnetogram. The technique provides a good sensitivity, also capable of discovering the following types of defects: i) Changing in geometry: dents, wavy surface, deformed shape of cross-section; ii) Metal loss, having mechanical, technological or corrosion nature; material discontinuity: layering and inclusions; iii) Cracks; iv) Welding flaws including girth weld defects. Moreover, such method provides a risk-factor (standard P 102-008-2002) ranking of the discovered pipe-line defects accordingly to material tension concentration (factor F). Accordingly this technique was taken as initial prototype for the disclosed technology.
MT determines the comparative degree of danger of defects by a direct quantitative assessment of the stress-deformed condition of the metal. Conventional surveys only measure the geometrical parameters of a defect. Their subsequent calculations to assess the impact of the defect on the safe operation of the pipe do not take into consideration the stress caused by the defect. Therefore conventional surveys may fail to detect dangerously stressed areas of the pipe or, conversely, classify a defect as one which requires urgent attention when, in reality, the stress level may be low and the defect presents no immediate threat to the operation of the pipe. Since MT directly measures the stress caused by defects it is an inherently more accurate guide to the safe operation of the pipeline than conventional survey methods.
There are several methods for integrity assessment of extended structures (e.g. metallic pipes) that have been proposed in literature. Thus, U.S. Pat. No. 4,998,208 (Buhrow, et al) discloses the piping corrosion monitoring system calculates the risk-level safety factor producing an inspection schedule. The proposed system runs on a personal computer and generates inspection dates for individual piping elements. Corrosion data for individual inspection points within each circuit is used to estimate likely corrosion rates for other elements of the particular circuit. It translates into risk factors such as the toxicity, the proximity to the valuable property, etc. The system evaluates a large number of possible corrosion mechanisms for each inspection point providing a very conservative inspection date schedule.
There is another method disclosed in U.S. Pat. No. 6,813,949 (Masaniello, et al.), which addresses a pipeline inspection system having a serviceability acceptance criteria for pipeline anomalies, specifically wrinkles, with an improved method of correlating ultrasonic test data to actual anomaly characteristics.
There is a also known procedure of planning a sequence of repair and renovation steps to be applied to the defective segments of heating infrastructures and buildings (RU 2110011 C1 (21) 95112182 (22) 13 Jul. 1995 published 27 Apr. 1998). This method offers Infra-red imaging of the constructions under testing, defining the defective areas, digitizing their images and evaluating the excessive heat produced by defective areas. The resulting data leads to the planning of a sequence of steps required for repairs.
The disadvantage of this method is a limited area of application where the heat-transferring objects, such as heating infrastructure, are present. Moreover, this method is effective only at the stage when the fracture and leakage have already been developed, causing the excessive heat radiation around the defective areas.
There are several methods for non-destructive testing of pipes have been known. Thus, US20060283251 (Hunaidi) suggests non-destructive condition assessment of a pipe carrying a fluid by evaluating the propagation velocity of an acoustic disturbance between two remote points on the pipe. A corresponding predicted value for the propagation velocity is computed as a function of the wall thickness.
Another non-destructive method U.S. Pat. No. 4,641,529 (Lorenzi, et al) discloses pipeline ultrasonic transducers in combination with photographic device for corrosion detection. Such ultrasonic transducer(s) produce a parallel beam for direction toward the pipe wall from inside a pipe, with a sufficiently large beam width to permit comparison of time displayed signal components in defect depth determination, with the signal propagating through a gaseous medium.
There is another method for estimating worst case corrosion in a pipeline is disclosed in U.S. Pat. No. 7,941,282 (Ziegel, et al), in which non-destructive pipeline wall thickness measurements are performed by sampled (at locations) ultrasonic and/or radiography (UT/RT) measurements. A distributed ILI data library for test pipelines is calibrated to correspond to UT/RT measurements for inspection. After sampling, the candidate statistical distributions are evaluated to determine which of the candidate most accurately estimates the worst case corrosion measured by ILI.
There is a known method for repair sequence planning based on possible (metal pipe) defects location and cause discovering by detecting anomalies in the magnetic field of pre-magnetized pipeline with special devices, such as pig-flow defectosopes, (RU No 2102652, 6F 17D5/00, published 1998).
Such method include a pipe-line setup with defectosope input-output chambers and a pig-flow device itself, as well as internal pipe-line surface cleaning means to provide the open cross-section needed to launch the pig-flow device. The method also requires a simultaneous magnetization of the pipe-wall along the pig-flow device movement and registration of anomalies based on scattering and saturation of the magnetic field, recording and processing of the information to conclude about defects location and nature.
As an example, another method can also be considered: RU2139515 filed Dec. 23, 1997). This method of evaluation of the material vulnerability and residual operation resource relies on the measured dependence between the mechanical (structural) defects (related to steel resistance) and steel parameters measured by non-destructive means, such as value of magnetic permeability measurement.
The, the technological outcome of present invention would include:
1) Expanding the implementation area, including not only the heating infrastructure and buildings but also various types of extended structures of metallic materials, including not-through defects in stage of development.
2) Increasing the reliability and accuracy of information about repair procedures suggested schedule. It can be done using the risk-factor ranking tables based on the absolute values of stress, compared against the values from regulatory documentation (for particular object).
3) Increasing the efficiency of the method by applying a visualization-assisted maintenance and repair schedule (with the real values of mechanical stress) to the actual structural layout, such as a pipe-line integrated into the existing topology, for example.
Such technological outcome can be achieved, mainly, due to the following innovative means: i) Remote (from the ground surface, non-destructive) identification of the defects and their respective risk-factors, by using improved measurements of the local mechanical stresses; ii) Remote identification of operational parameters for the defective segments of the structure, by using the absolute local stress values, compared against the values from regulatory documentation (for particular object). iii) Graphical visualization of the obtained information using the actual topological layout of the area and the structure in absolute geographical coordinates.